1 Original Research Article 2 3 Diversity and distribution of Vascular epiphytic flora in Sub-temperate forests of 4 Darjeeling Himalaya, India 5 6 Preshina Rai1 & Saurav Moktan2* 7 1Department of Botany, University of Calcutta, 35, B.C. Road, Kolkata-700 019, India 8 2*Department of Botany, University of Calcutta, 35, B.C. Road, Kolkata-700 019, India 9 10 ABSTRACT 11 Aims: This communication deals with the diversity and distribution including host species distribution of 12 vascular epiphytes also reflecting its phenological observations. 13 Study design: Random field survey was carried out in the study site to identify and record the taxa. Host 14 species was identified and vascular epiphytes were noted. 15 Study site and duration: The study was conducted in the sub-temperate forests of Darjeeling Himalaya 16 this is a part of the eastern Himalaya hotspot. The zone extends between 1200 to 1850 m amsl 17 representing the amalgamation of both sub-tropical and temperate vegetation. The study was conducted 18 during the year 2018-2019. 19 Methodology: Process of random sampling collection was followed. Host trees with CBH >30 cm were 20 identified and percentage of distribution of epiphytes in the host tree was analyzed and divided into two 21 zones depending on the abundance of epiphytes. Data for the epiphytic plant specimens were collected 22 in the field. Exsiccates were made with the collected voucher specimens and were deposited at the 23 Calcutta University Herbarium (CUH) following the conventional methodology. Study on the taxa are 24 based on their host tree distribution, micro-habitat and phenological status. The location and altitude of 25 the study sites were recorded by global positioning system. 26 Results: A total number of 115 species under 70 genera and 31 families have been identified with 65 % 27 other vascular angiosperms (basal angiosperms and eudicots) and 16 % monocots. Orchidaceae among 28 the monocots represented 36 % with 41 species and 18 genera. Ferns and lycophytes include 25 % of 29 the diversity with 29 taxa under 6 families. Most favorable host trees were Ficus auriculata Lour., Ficus 30 neriifolia Sm., Saurauia nepalensis DC., Erythrina variegata L., Macaranga denticulata (Blume) 31 Müll.Arg., Cryptomeria japonica (Thunb. ex L.f.) D. Don and Engelhardia spicata Lechen ex Blume. 32 Conclusion: The other vascular angiosperms preferred wet monsoon for flowering whereas spring 33 season was most favourable for Orchidaceae. Although a healthy number of vascular epiphytes have 34 been identified, a number of threats are still prevailing in the regions which are mostly anthropogenic. 35 Proper collaborative strategies have to be maintained for its conservation. 36 Keywords: Vascular angiosperm, phenology, orchidaceae, host tree, conservation 37 38 1. INTRODUCTION 39 Originally, the name epiphyte is derived from two Greek words ‘epi=upon and phyton=plants’ [1]. 40 Epiphyte may be defined as a plant that root and perch on the surface of another plant or non living 41 objects without driving food from its host [2, 3, 4, 5]. They are a unique and diverse group of plants with 42 very interesting ecology [6] comprising about 10 % of the world’s total flora [7]. Epiphytes are 43 taxonomically heterogeneous group composed of over 28,000 species under 84 families and represent 44 an important proportion of world flora [8, 9]. They may be divided into holo-epiphytes, primary hemi- 45 epiphytes, and secondary hemi-epiphytes functional types [10]. Holoepiphytes never have root contact 46 with the soil while hemi-epiphytes are connected to the soil during part of their life-cycle at which stage 47 they resemble vines (i.e. herbaceous climbers). Primary hemi-epiphytes germinate on other plants, 48 usually trees, only to become terrestrially-rooted through aerial roots while secondary hemi-epiphytes 49 germinate in the soil to lose contact later. They contribute to the richness of local and regional floristic 50 diversity Microhabitats on trees trunks, barks and irregular surfaces on branches are all favourable for 51 the growth of epiphytes [11]. Epiphytes ecologically contribute to forest biodiversity in increasing species 52 richness [12], primary productivity, biomass, water retention and also provide substrate for nitrogen fixing 53 bacteria and serve as indicators of change in microclimate as well as global climatic change [13, 14] 54 including nutrient store [15]. They also provide food and shelter for fauna [16]. Some angiospermic 55 epiphytes have ethnomedicinal uses and are used against several ailments [17]. Vascular epiphytes are 56 vulnerable group and consequently represent a good indicator group of biodiversity that can be 2 57 monitored to assess the effects of forest disturbance [18]. Many vascular epiphytes exhibit physiological 58 and morphological characteristics that help them survive drought [19] and also assist in water retention, 59 such as thickened or succulent leaves, or rhizomes and specialized water storage tissue [4, 6, 20, 21, 60 22]. The vascular epiphytes are sensitive to moisture which makes them a good environmental indicator 61 for both successional stages of forest ecosystems and natural environmental variations [23, 24]. The 62 communities of vascular epiphytes have been used as bio-indicators of climate change, pollution and 63 damage to ecosystems [25, 26, 27]. This sensitivity becomes important in the context of conservation, 64 given that many of the epiphytic species have a high degree of specialization with their phorophyte, thus 65 becoming vulnerable to extinction by habitat and climate change [28, 29]. Vascular epiphytes in majority 66 comprise of fern and monocots - especially orchids, bromeliads and aroids with relatively fewer other 67 angiosperms [30]. Phorophyte structure, substrate availability and dispersal syndromes are main factors 68 for distribution pattern of vascular epiphytes [31, 32]. Besides, establishment of vascular epiphytes 69 provide suitable niche through autogenic succession to other epiphytes (33). The species of vascular 70 epiphytes are increasingly threatened and decrease in population due to over-collecting horticulturally 71 valuable species for commercial purposes and habitat loss due to deforestation and land use changes 72 [30]. Works related to epiphytes have been conducted in Western ghats [34, 35, 36], Western Himalayas 73 [37, 38, 39, 40], Central Himalayas [41, 42, 43] as well as towards the Eastern Himalaya [44, 45, 46, 47]. 74 Although, several workers have explored the flora of Darjeeling Himalaya [48, 49, 50, 51, 52, 53, 54], 75 only few notable works with particular reference to vascular epiphytes are known [45, 46]. Therefore, 76 there is a need to investigate and understand the rich vascular epiphytic flora from Darjeeling region of 77 eastern Himalaya. 78 79 2. METHODOLOGY 80 2.1. Study Area 81 The present study was conducted in the Sub-temperate forests of Darjeeling Himalaya. The Darjeeling 82 Himalaya extends between 27° 13' 10'' N to 26° 27' 05'' N Latitude and 88° 53' E to 87° 59' 30'' E 83 Longitude that is located in India’s state West Bengal, in the Himalayan foothills at an altitudinal range of 84 130 to 3636 m amsl. It is situated at the northernmost end of the Eastern India in the form of an inverted 3 85 wedge, covering about 3.68 % of the total area of the state of West Bengal. The northernmost point of 86 the district is the tri-junction near Phalut [27° 13' 10'' N; 88° 21' E] and the southern-most point is the 87 Phansidewa block [26° 27' 05'' N; 88° 22' E]; likewise the west to east extension of the district lies 88 between Sabarkum near Sandakphu [87° 59' 30'' E; 27° 12' N] and Todey village along river Jaldhaka 89 [88° 53' E; 27° 04' N]. Due to the altitudinal variation that range from tropical plain to sub-alpine zone, 90 different climatic zones are available in Darjeeling Himalaya which offers favourable environment for the 91 growth and development of all plant species including epiphytes and their migration in different habitats 92 [52]. The Sub-temperate vegetation zone has been classified between 1200 to 1850 m amsl and 93 represents the amalgamation of both the sub-tropical and temperate vegetation with intermediate type of 94 forest composition. The climatic set-up of four seasons are recognized in the region: (i) Winter from 95 December to February, (ii) Spring and summer from March to May, (iii) Monsoon or Rainy Season from 96 June to August, and (iv) Autumn from September to November [51]. The temperature in the region varies 97 with a minimum of 2.4°C to a maximum of 9.6°C during winter, 8.3°C to 19.1°C during spring and 98 summer and 12°C to 18°C during autumn season with an average annual precipitation of about 337.3 99 mm. 100 2.2. Data Collection 101 Field survey was carried out from October 2018 to October 2019 in the forest that lied within the Sub- 102 temperate altitude. The process of random sampling collection was followed. Some of the areas under 103 study include Bagora [26º 9378' N, 88º 3127' E], Lower Mamring [26º 56.557' N 88º 20.018' E], Oneblock 104 [26º 56.302' N 88º 19.134' E], Chimney [26º 55.384' N 88º 18.699' E], Chattakpur [26º 9671' N 88º 2112' 105 E], Latpanchor [26º 9159' N 88º 4028' E], Mahaldiram [26º 9224' N 88º 3288' E] and areas where the 106 diversity of vascular epiphytes was rich (Fig. 1). 107 Data on abundance of epiphytic plant specimens were collected in the field with the assistance of local 108 tree climber; epiphytic plants were collected both from the ground and tree. Host tree species with >30 109 cm CBH were identified and sampled randomly in the forest and segregated into two zones i) Trunk zone 110 covering the area below the first branching till the base and ii) Inner crown zone covering the remaining 111 area above the first branching (Fig.